In my program I already have an expression (char array) so I don't want to use the "cin" commands (especialy cin.putback) to deal with the expression..
I want to use my array or maybe put the string into cin streaming function(if possible) so I'll can use this code..
Any ideas..?
Thanks for your help.

Who is Participating?

The idea is similar to that, you used in your code.
Program is goint through array of chars and checking
for arrays of successive digits (numbers) and puting
them in an array of numbers. At the end program prints
the first of them.

// i is index of current character in array
// len is length of array
// number is array if numbers found in array
// num is current number
// ntop is index of current number

cout << "And the answer is: " << number[0] << endl;

// note that if there is no numbers in array
// number[0] will be some random number.

// this is is optional, just to show you
// that program is correct.
cout << "Other numbers: ";
for (int i = 1; i < ntop; i++)
cout << number [i] << " ";
cout << endl;
}
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Looks like you would like to convert your char array to the array of numbers as in the small example.
Would this be helpful:
for(int i=0;...) {
number[i] = atoi(yourCharArr[i]; //for int atof for double
}
Now you have numbers instead of characters if that was what you tried to achieve